This section provides background information to facilitate a better understanding of the various aspects of the invention. It should be understood that the statements in this section of this document are to be read in this light, and not as admissions of prior art.
The invention relates in general to marine seismic systems and in particular to devices and methods for positioning tows (e.g., seismic streamer or seismic source) in the water relative to the tow vessel and one another to efficiently conduct marine seismic surveys and to acquire accurate and high quality seismic data.
Marine seismic exploration investigates and maps the structure and character of subsurface geological formations underlying a body of water. For large survey areas, seismic vessels tow one or more seismic sources and multiple seismic streamer cables through the water. The seismic sources typically comprise compressed air guns for generating acoustic pulses in the water. The energy from these pulses propagates downwardly into the geological formations and is reflected upwardly from the interfaces between subsurface geological formations. The reflected energy is sensed with hydrophones attached to the seismic streamers, and data representing such energy is recorded and processed to provide information about the underlying geological features.
Three-dimensional (3-D) seismic surveys of a grid gather data utilized to generate geophysical maps of subsurface formations that include longitudinal, lateral and depth information. Four-dimensional (4-D) mapping utilizes two or more 3-D seismic surveys conducted over time to reveal changes in the subsurface formations over time, for example, by the extraction of oil and gas. Since the grid is often much wider than the towed streamer array, the tow vessel must turn around and tow the streamer array in laps across the grid, being careful not to overlap or leave large gaps between the laps across the grid. The quality of the data recorded by the streamer receivers and the quality of the 3-D or 4-D geophysical images is dependent on how accurately the tow members (e.g., source equipment and streamers) are positioned. In this context, the term positioned refers to how each tow member is positioned relative to the other tow members, for example in the in-line (i.e., longitudinal) and the cross-line (i.e., lateral) directions.
There is a continuing desire to acquire accurate, high quality seismic data efficiently. According to one or more aspects of the disclosure, it is a desire to provide a system and method for deploying and positioning marine seismic tows. According to one or more aspects of the disclosure, it is a desire to provide a system and method for deploying seismic tows from a common carrier rope and facilitating independent positioning of one or more of the seismic tows relative to one or more of the other seismic tows.